1. Field of the Invention
The present invention generally relates to a secondary battery remaining capacity estimating apparatus for estimating a remaining capacity of a secondary battery.
2. Background Information
There are basically two main methods for estimating the remaining capacity of a battery. The first is to estimate the remaining capacity of the battery by integrating a current value (hereinafter called a “current integration method”). The other is to use a relationship between an open circuit voltage and the remaining battery capacity to estimate the remaining capacity of the battery based on the open circuit voltage (hereinafter called an “open circuit voltage method”). However, both of these estimation methods have advantages and disadvantages. Japanese Patent Publication No. 3640142 discloses a battery remaining capacity indicating apparatus that selects between the two methods just described in accordance with a condition of the secondary battery and estimate the remaining capacity of the battery using the selected method. The battery remaining capacity indicating apparatus calculates a difference between an estimation value obtained using the current integration method and an estimation value obtained using the open circuit voltage method and compares the difference to a prescribed value. If the difference is below the prescribed value, then the estimation value obtained using the current integration method is indicated as the remaining capacity of the battery. If the difference is above the prescribed value, then the estimation value obtained using the current integration method is gradually decreased and the decreased estimation value is indicated as the remaining capacity of the battery In this way, a more accurate estimation of the remaining capacity of the battery can be indicated.